Planar lightwave circuit

Abstract

In an integrated optical receiver or transmitter, both the displacement of an optical axis caused by thermal changes and the property degradation of an optical functional circuit are inhibited. A planar lightwave circuit having a substrate and a waveguide-type optical functional circuit formed thereon composed of a material different from that of the substrate, and includes a waveguide region formed only of an optical wavelength that is in contact with a side forming an emission-end face of the optical waveguide for propagating the light emitted from the optical functional circuit or an incident-end face of an optical waveguide for propagating the light incident on the optical functional circuit. The planar lightwave circuit is fixed to a fixing mount only at the bottom of the substrate where the waveguide region is formed.

What is claimed is: 
     
       1. A planar lightwave circuit having a waveguide-type optical functional circuit formed on a substrate, the planar lightwave circuit comprising:
 a region that includes an optical functional circuit; and 
 a waveguide region that only includes an optical waveguide that is in contact with an end of the substrate, the waveguide region forming an end face that is either an emission-end face of the optical waveguide for propagating light emitted from the optical functional circuit or an incident-end face of the optical waveguide for propagating light incident on the optical functional circuit, 
 wherein the portion of the substrate on which the waveguide region is only formed is fixed to a fixing mount for holding the planar lightwave circuit such that only one end of the substrate is fixed to the fixing mount, 
 wherein the region that includes the optical functional circuit is not fixed to the fixing mount and has a shape which is changed as desired regardless of any warping due to thermal changes. 
 
     
     
       2. The planar lightwave circuit according to  claim 1 , wherein the end face is vertically oblique with respect to a circuit plane of the planar lightwave circuit. 
     
     
       3. The planar lightwave circuit according to  claim 1 , wherein the substrate is thermally coupled to the fixing mount through a heat conductive paste. 
     
     
       4. An optical device comprising:
 a planar lightwave circuit comprising:
 a substrate having opposing top and bottom surfaces; and 
 a waveguide-type optical functional circuit formed on the top surface of the substrate, the waveguide-type optical functional circuit having an end face for propagating light thereto or therefrom, the waveguide-type optical functional circuit comprising:
 a first region positioned on a first portion of the substrate, the first region comprising an optical waveguide abutting the end face; and 
 a second region positioned on a second portion of the substrate; and 
 
 
 a fixing mount on which the planar lightwave circuit is mounted, the bottom of the first portion of the substrate being the only portion of the planar lightwave circuit fixed to the fixing mount to hold the planar lightwave circuit so that only one end of the substrate is fixed to the fixing mount, wherein the first region of the waveguide-type optical functional circuit has a shape which is changed as desired regardless of any warping due to thermal changes. 
 
     
     
       5. The planar lightwave circuit according to  claim 4 , wherein the end face is vertically oblique with respect to a top surface of the planar lightwave circuit. 
     
     
       6. The planar lightwave circuit according to  claim 4 , wherein the substrate is thermally coupled to the fixing mount through a heat conductive paste. 
     
     
       7. The planar lightwave circuit according to  claim 4 , wherein the second region comprises an optical interferometer. 
     
     
       8. An optical device comprising:
 a planar lightwave circuit extending from a first end to a second end, the planar lightwave circuit comprising:
 a substrate having opposing top and bottom surfaces, the substrate having a first portion and a second portion positioned respectively at the first and second ends; and 
 a waveguide-type optical functional circuit formed on the top surface of the substrate, the waveguide-type optical functional circuit having an end face positioned at the first end for propagating light thereto or therefrom, the waveguide-type optical functional circuit comprising:
 a first region positioned on the first portion of the substrate, the first region comprising an optical waveguide abutting the end face; and 
 a second region positioned on the second portion of the substrate; and 
 
 
 a fixing mount on which the planar lightwave circuit is mounted, the first portion of the substrate being fixed to the fixing mount and the second portion of the substrate not being fixed to the fixing mount so that only one end of the planar lightwave circuit is fixed to the fixing mount, wherein the first region of the waveguide-type optical functional circuit has a shape which is changed as desired regardless of any warping due to thermal changes. 
 
     
     
       9. The planar lightwave circuit according to  claim 8 , wherein the substrate is thermally coupled to the fixing mount through a heat conductive paste. 
     
     
       10. The planar lightwave circuit according to  claim 8 , wherein the second region comprises an optical interferometer. 
     
     
       11. The planar lightwave circuit according to  claim 8 , further comprising a fiber fixing component attached to the second end of the planar lightwave circuit, the fiber fixing component being adapted to receive an optical fiber.